Tab welded joint and method of making

ABSTRACT

A welded joint comprising overlapped strips of metal with tabs formed by piercing or lancing through the overlapped portion. The formed tabs are flattened against the metal and resistance spot welded to such metal. The resistance welding forms a metallurgical bond between the metal members.

I Umted States Patent 1151 3,640,556 Bennett Feb. 8, 1972 [54] TABWELDED JOINT AND METHOD OF 3,247,316 4/1966 Weimer ..174/94 MAKING3,278,880 10/1966 Lewis et al.... ..336/192 3,281,923 11/1966 Best etal. ..29/470.5 X 1 lnvemofl Mordqnd Bennett, 45 Concord Park- 2,149,8443/1939 George ..287/l 89.36 8 Mass- 01201 2,814,810 12/1957 Kelly..287/l89.36 B x [22] Filed: Aug. 22, 1969 Primary ExaminerDavid J.Wilhamowsky [21] Appl' 868,259 Assistant Examinerwayne L. SheddAttorney-Gilbert P. Tarleton, Francis X. Doyle, Melvin A. Rem! Amman DamGoldenberg, Frank L. Neuhauser and Oscar B. Waddell [62] Division ofSer. No. 616,945, Feb. 17, 1967.

[57] ABSTRACT [52] US. CL ..287/ 189.3613, 29/432, 29/4705,

29/509 29/513, 219/91 219/92 A welded 1011112 comprising overlappedstnps of metal w1th tabs 51 1 m1. (:1 ..F16b 5/07, F16b 5/08 frmed byPiercing aiming through mflapped [58] Field of Search ..287/189, 36 B;219/91, 92, The formed tabs are flattened against the metal andresistance 219/93; 24/4705 509 5 3 spot welded to such metal. Theresistance welding forms a metallurgical bond between the metal members.

[56] References Cited 6 Cl 5 Dn Figures UNITED STATES PATENTS 2,190,6212/1940 Baer ..219/91 TAB WELDED JOINT AND METHOD OF MAKING This is adivision of application Ser. No. 616,945, filed Feb. 17, 1967, which isassigned to the same assignee as this present application.

BACKGROUND OF THE INVENTION This invention relates to metal joints andmore particularly to a welded joint and the method of making such joint.The joints of this invention find special utility in the electricalindustry.

As is well known to those skilled in the metal joining art, it is oftennecessary to joint metal members to provide not only a secure mechanicaljoint, but one which will provide a sound electrical connection. Thesetypes of joints are usually required in the electrical industry forsecuring electrical conductive members to each other. One well-knownconnection which must be both mechanically secure and electrically soundis the connection made between the lead or tap strap and an electricalcoil. In many modern day coils a very thin foil is used for the coilwinding with somewhat thicker strip material used for leads or tapstraps. In many coils, the winding is made of one metallic material suchas aluminum while the leads or tap straps are made of another metallicmaterial such as copper. Much difficulty has been experienced inproviding adequate mechanical and electrical connections between thefoil wound coils and the leads or tap straps.

Mechanical connections are usually formed by riveting or crimping andare generally undesirable because they depend solely on the contactbetween adjacent surfaces for transmission of electrical current. Asthese joints age, the connections tend to relax and oxides may form onthe adjacent surfaces, providing very poor electrical connections.Solder connections are not useful for high current uses since the solderhas a very low melting temperature. Further, there is no metallurgicalbond between the solder and the joint surfaces, which often leads to apoor electrical connection. Brazing and welding of joints require anexpensive cleaning process and also are very difficult to make withoutdamage to the thin foils. It has recently been discovered that thinfoils and strips of similar and dissimilar metals may be joined in astrong mechanical and electrical connection by piercing tabs in themetal and spot welding the formed tabs.

SUMMARY OF INVENTION It is therefore one object of this invention toprovide a welded joint for joining thin foil and strips of metal.

A further object of this invention is to provide a method of making amechanical weld joint between thin metal members.

A still further object of this invention is to provide a mechanical weldjoint for metal members.

In carrying out this invention in one form, metal members to be joinedare placed in overlapping relation. Tabs are formed through theoverlapped portions of the metal members, the formed tabs are flattenedand then spot welded to one of the metal members. The spot welding formsa metallurgical bond between the tab and the various metal members.

The invention sought to be protected will be particularly pointed outand distinctly claimed in the claims appended hereto. However, it isbelieved that this invention and the manner in which its various objectsand advantages are obtained as well as other objects and advantagesthereof, may be better understood from the following detaileddescription of a preferred embodiment especially when considered inconjunction with the accompanying drawing.

BRIEF DESCRIPTION OF DRAWING FIG. 1 is a perspective view of a preferredjoint made according to this invention;

FIG. 2 is a top view of the joint shown in FIG. 1;

FIG. 3 is an enlarged sectional view of metal members to be joinedshowing the preferred method of this invention;

FIG. 4 is an enlarged sectional view of a completed joint made according to this invention; and

FIG. 5 is an enlarged sectional view of a completed joint made accordingto another embodiment of this invention.

DESCRIPTION OF PREFERRED EMBODIMENTS As above noted, it has beendiscovered that thin foils and strips of metal may be joined by usingtabs formed in overlapped portions of the metal members and then spotwelding the tabs to one of the metal members. The metals to be joinedare placed in overlapped relation and a plurality of tabs are formedthrough the overlapped portions. A resistance spot welder is thenapplied to opposite sides of the joint flattening the tabs and weldingthem to the metal. The welding step metallurgically bonds the metalstogether providing a good electrical connection strengthened by theformed and welded tabs. In a preferred form of joint, a pair ofrelatively thicker strips are placed on each side of a foil memberproviding a joint which is mechanically stronger than can be obtained bya single strip and foil member.

Where copper and aluminum are to be joined by a method of thisinvention, it is found desirable to first tin-plate the copper and thento provide copper on each side of the aluminum. Of course, the coppercould be silver-plated, if desired. However, from the cost view,tin-plating is preferred. This will provide a better metallurgical bondbetween the copper and the aluminum. Referring now to the drawings, inwhich like numerals are used to indicate like parts throughout thevarious views, FIG. 1 shows a perspective view of a preferred joint madeaccording to this invention. As shown in FIG. 1, a joint is formedbetween a metal foil member 10 and a pair of thin metal strips 12 and14. The metal strips 12 and 14 are placed on opposite sides of the foil10. The three metal members have overlapped portions as shown. As can beseen, a plurality of tabs 16 are formed through the overlapped portionsof the metal members l0, l2 and 14. As is shown, particularly in FIG,.2, the tabs 16 are preferably of substantially triangular shape, leavingthe triangular holes 18 through the overlapped metal portions. The tabsare flattened against the top metal strip 12 and welded thereto as willbe more fully discussed with reference to FIG. 3.

FIG. 3 shows the preferred method of making the joint of this invention.FIG. 3 is an enlarged sectional view showing a tab 16 pierced or lancedfrom the three overlapped portions of the foil 10 and the metal strips12 and 14. As is apparent from FIG. 3, tab 16 is formed from parts ofeach metal member and has been folded over the top of the strip 12. Aresistance spot welder indicated by electrodes 20 and 22, is thenbrought in contact with opposite sides of the overlapped metal membersl0, l2 and 14 at the tab 16 as indicated. The welder is energized by asource of electrical energy indicated at 24, such that when electrodes20 and 22 contact the overlapped metal members, current will flowthrough the metal members to weld the members together. Sufficientpressure is applied by electrodes 20 and 22 as indicated by the arrowsto flatten tab 16 against the metal strip 12. It is preferred to userefractory or other high-resistance electrodes so that the electrodesprovide the major heating for welding the joint.

A portion of a completed joint is shown in enlarged sectional view inFIG. 4. As can be seen in FIG. 4, the heat and pressure from the weldingelectrodes 20 and 22 has forced the tab 16 into the surface of the strip12, welding the metal parts of tab 16 to each other and to the strip 12.The welding heat has also substantially welded the metal members l0, l2and 14 to each other in the area of tab 16 as is shown by the drawing inFIG. 4. Of course, it will be apparent that each tab in the joinedsurfaces will be similarly welded and that as many tabs as desired maybe provided.

In a test of this invention, a pair of joints were made, each joint wasformed of two strips of 0.010 inch thick copper 0.75 inch wide with a l0inch portion of 0.006 inch aluminum foil secured between the copperstrips. The copper for both joints were tin plated. One joint was madewith seven tabs, while the 1 other joint was made with 13 tabs. Thejoints were welded with the current of approximately 4,000 amperes and apressure of approximately 75 pounds. Both joints were subjected to pulltests and to heat and short circuit tests. Both joints exhibitedsatisfactory strength, sustaining a tensile pull of approximately 90pounds. The joints also passed 18 times normal current for 3.5 seconds.In the heat test the seven-tab joint ran approximately C. hotter thanthe l3-tab joint. However, both joints were considered adequate for usein connecting lead wires to coils.

FIG. 5 shows a completed joint made between a single strip of metal anda piece of foil, according to another embodiment of this invention. Thisform of the invention is especially useful when the foil member has beencoated with insulation. As is shown in FIG. 5, a foil member 30,provided with insulation 32 is joined to a metal strip 34. A tab 36 hasbeen struck from the overlapped metals, leaving an opening 38. Tab 36 isthen flattened against the insulation 32 on foil 30. Then a resistancespot welder, such as is indicated in FIG,. 3, is applied to oppositesides of the metal members 30, 34 at tab 36. The heat and pressureprovided by the resistance spot welder burns off the insulation 32beneath tab 36 and welds foil 30 and strip 34 together, as shown. Thismethod provides very good electrical joints between a lead and a foilwinding without the necessity of removing the insulation prior to makingthe joint.

While there has been shown and described the present preferredembodiments of this invention, it will be clear that .various changesmay be made by those skilled in this art. For

example, it will be apparent that sections of foil may be connected toeach other by a metal strip by use of this invention. Other changes oruses may also be made by those skilled in this art without departingfrom the spirit and scope of the invention, particularly as defined inthe appended claims.

What is claimed as new and which it is desired to be secured by LettersPatent of the United States is:

17 A welded metal joint between a metal foil member and at least onemetal strip member, said metal members having portions in overlappedspatial contacting relation comprising; a plurality of tabs, each ofsaid plurality of tabs having superposed material of said metal membersand being bent together over the uppermost metal member, said pluralityof tabs being welded to said uppermost metal member.

2. A welded metal joint as claimed in claim 1 which said foil is coatedwith insulation, said insulation burned off below said plurality ofwelded tabs.

3. A welded metal joint as claimed in claim 1 in which a pair of metalstrips are provided, one metal strip on each side of said metal foil.

4. A welded metal joint as claimed in claim 1 in which said metal foilis aluminum and said metal strip is copper.

5. A welded metal joint as claimed in claim 3 in which said metal foilis aluminum and said pair of metal strips are copper.

6. A welded joint as claimed in claim 5 in which said copper is tinplated.

Patent 3,640,556 v v Dated February 8, 1972 r Moreland P Bennett inver;tor(s) It is certified that error appears in the above-identified patentand that said Letters Patent are hereby corrected as. shown-below:

' On the cover sheet, insert [73 Assignee: General Electric Company, acorporation of New York Signed and sealed this 14th dayof November 1972.

(SEAL) Attest:

EDWARD MTLETCHERJR. ROBERT GOTTSCHALK Attesting Officer Commissioner ofPatents FORM PO-IOSO (10-69) uscoMM-oc 60376-P69 fi US. GOVERNMENTPRINTING OFFICE: I989 0-366-334;

Patent 3,640,556 Dated February 8, 1972 Moreland P Bennett inver.tor(s)It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shownbelow:

On the cover sheet, insert [73 Assignee: General Electric Company, acorporation of New York a Signed and sealed this 14th day of November1972.

(SEAL) Attest:

EDWARD I -I.FLETCHER,JR. ROBERT GOTTSCHALK Attesting OfficerCommissioner of Patents FORM o-1050 (10-69) uscoMM-oc scam-ps9 fi U.SGOVERNMENT PRINTING OFFICE I965 D-356-334

1. A welded metal joint between a metal foil member and at least onemetal strip member, said metal members having portions in overlappedspatial contacting relation comprising; a plurality of tabs, each ofsaid plurality of tabs having superposed material of said metal membersand being bent together over the uppermost metal member, said pluralityof tabs being welded to said uppermost metal member.
 2. A welded metaljoint as claimed in claim 1 which said foil is coated with insulation,said insulation burned off below said plurality of welded tabs.
 3. Awelded metal joint as claimed in claim 1 in which a pair of metal stripsare provided, one metal strIp on each side of said metal foil.
 4. Awelded metal joint as claimed in claim 1 in which said metal foil isaluminum and said metal strip is copper.
 5. A welded metal joint asclaimed in claim 3 in which said metal foil is aluminum and said pair ofmetal strips are copper.
 6. A welded joint as claimed in claim 5 inwhich said copper is tin plated.